Problem with .then off a javascript async function

I ran into a weird problem with a .then off an asyc function’s promise.
I call to a function to check the user’s google id against my database to see if they have an account on the network.

Login(DecodedGoogleCredentials.sub).then((localID)=> {//Login returns a promise with the local id for the database

             console.log(localID);//used to confirm id
             sessionStorage.setItem("CurrentUserID", localID);//set for refresh

             setID(localID);//set to recall App
             setLogin(true);//set to ensure it will be recalled

       });//end of Login().then(()=>{});

In my asnc function, I get the local id I expect, but when I check it with console.log(localID); in my .then, it writes a result of undefined.

Here is the async function:

async function Login(GoogleID) {//Called from App()
    
    const idQuery = query(idRef, where("id", "==", GoogleID.toString()));//build query for user's id
    const idDoc = await getDocs(idQuery);//get doc found in query. There should only be one
    
    var userFound = false;//user is not found
    
    idDoc.forEach((doc) => {//loop through docs

        userFound = true;//user is found  
        const localID = doc.data().localID;
        console.log(localID)
        try {
            return localID;
        }
        catch(e) {
            console.log(e)
        }
        
    });
    //there is no user so far
    if (userFound==false) {//create new user if user is not found
        
       return await CreateUser(GoogleID);//create the login
    }
}//end of Login(id)

The console.log(localID) here works perfectly and writes the value that I expect. Anyone know why I’m getting a different result in my .then function?

Answer:

Thanks everyone for your help. The problem stemmed from me returning from a foreach.
here is what my new code looks like, which functions correctly

async function Login(GoogleID) {//Called from App()
    
    const idQuery = query(idRef, where("id", "==", GoogleID.toString()));//build query for user's id
    const idDoc = await getDocs(idQuery);//get doc found in query. There should only be one

    var foundDoc;
    idDoc.forEach((doc) => {//loop through docs
       foundDoc = doc
    });
    if (foundDoc != null) {
        const localID = foundDoc.data().localID;
        
       
            return localID;
        
    }
   else {//create new user if user is not found
        
       return CreateUser(GoogleID);//create the login
    }
}//end of Login(id)

>Solution :

The return statement in the forEach loop exists the function you are passing to it, and not the main Login function.

Also the try/catch around it is useless, since return followed by a variable will never throw.

Consider using Array.prototype.find instead:

async function login(id) {
    const idQuery = query(idRef, where("id", "==", id.toString()));
    const idDoc = await getDocs(idQuery);
    const foundID = idDoc.find((doc) => doc.data().localID);
    if (foundID) {
        return foundID;
    }
    return CreateUser(id);
}